Containers and related devices



MaI'Ch 1953 M. A. COLE-R CONTAINERS AND RELATED DEVICES Original FiledNov. 15, 1951 RADIO FREQU ENCY GENERATOR INVENTOR. MYRON A, COLER BY 4AG ENT g5.

FIG.5

CONTAINERS AND RELATED DEVICES Myron A. Coler, New York, N. Y.

Original application November 15, 1951, Serial No. 256,518. Divided andthis application July 19, 1954, Serial No. 444,035

7 Claims. (Cl. 13683) This invention relates to electrochemical batterycells and in particular to containers for same.

This application is a continuation of my copending application entitledContainers and Related Devices, filed November 15, 1951, and assignedSerial Number 256,518.

A problem which has long plagued designers of electrical equipment andof packages for the same has been the one of finding methods foreffecting electrical contact through walls of insulating plasticmaterial. This is a particular case of the still more general problem ofsecuring a tight casing through which electrical contact may be made tomaterial or equipment inside said casing.

Attempts to fabricate tight casings for electrical equipment generallybreak down into instances-where the casing is predominantly metallic orpredominantly insulator.

in the former case it is usually necessary to introduce more than oneelectrical connection to the interior of the casing. Usually at leastone such connection must be insulated from the main casing body. Thepresence of the insulator invariably introduces problems associated withdifferences between the physical properties, especially the thermalexpansion, of insulator and metal.

in some cases rubber insulated wire is passed through holes in the metalcasing after which an attempt is made to tighten the seal by means ofvarious kinds of clamps or packing glands. Such glands involve screwedor split parts which are seldom completely tight. The point of clampingthe wire is a site for wear and fatigue. Flexible insulation and packingmaterials are subject to fairly rapid deterioration.

in another attempted solution of the problem, the parts of a metalcasing are themselves used to carry electrical energy to or from theinterior of the casing. This necessarily implies that certain parts ofthe casing are insulated from one another. Thus, for instance, twohalves of a metal casing for an electrochemical cell system may beshaped from sheet metal and the edges of the two halves crimped togetherover an insulating gasket. Such seals are found in practice to besubject to rather frequent failure.

In general, the longer the line of contact between metal and insulatormaterial, the greater the difficulty in obtaining a tight seal. Thus,the common method of sealing a Leclanche cell by casting an insulatingwax into the top of a zinc case is particularly subject to leakage underthe stress of changing temperature.

The attempt to seal a structure which is made predominantly of insulatormaterial with metal contacts likewise meets with practical difficulties.

The passage of metal contacts, such as wires, through a plastic bodymeets with the same difficulties due to dif ferences in thermalexpanision as exist in the converse arrangement.

There is disclosed herein a simple, effective and economical means forsecuring electrical connection across a tight casing wall by creating anintegral bond between an electrically conductive composition plasticmaterial and Patented Mar. 4, 1958 ice an insulator plastic thusavoiding the many cited drawbacks of the prior art.

It is therefore an object of this invention to provide liquid tightbattery casings through which electrical connection can be made.

It is a specific object of this invention to provide allplastic liquidtight battery cell casings.

it is a more specific object of this invention to provide all-plasticliquid tight battery cell casings, portions of which serve as electrodesof the electrochemical cell system.

Other general and specific objects of this invention will becomeapparent upon perusal of the appended specifications.

For a mor complete understanding of my invention, reference should nowbe made to the accompanying description taken in conjunction with thedrawings in which:

Figure l is a cross-sectional view in elevation of a battery of thisinvention.

Figure 2 shows a preferred method of forming a highly conductiveterminal.

Figure 3 shows in perspective an embodiment of this invention in theform of a sealed container and a preferred method of sealing same.

Figure 4 is a cross-sectional view in elevation of another battery ofthis invention.

Figure 5 is a cross-sectional view of a standard zinccarbon dry cell ina casing of this invention.

As is well known, there exist numerous electrically conductive plasticcompositions which are made by blending finely divided electricallyconductive materials such as graphite and metals with insulatorplastics. I have found that these materials correspond closely in theirphysical properties (aside from appearance and electrical conductivity)with the parent insulator plastics from which they are made. Of course,if the loading with conductive filler is very high, the strength andcertain other properties of the plastic will be materially affected justas they will be by the inclusion of more common fillers.

In any case, I have found that the conductive plastic compositions canbe securely bonded by various methods detailed below to thecorresponding insulator plastic from which they were made. Such bonds,being between materials possessing very similar coeflicients of thermalexpansion, are not subject to great stress when passed through cycles ofchanging temperature.

Electrically conductive plastics made according to the copendingapplication of Myron A. Coler entitled Metallized Plastics, SerialNumber 735,553, filed March 18, 1947, now abandoned, are particularlysuited to the purposes of the present invention because they possessmuch higher conductivity for a given content of conductive material thanother known electrically conductive plastic compositions. Consequently,their general physical properties depart less from those of their parentplastics than do the properties of other conductive plastic compositionspossessing the same degress of electrical conductivity.

Furthermore, be it noted that, by the use of techniques described in theco-pending application of Myron A. Coler and Arnold 5. Louis entitledComposite Plastic Articles and Method of Making Same, Serial Number256,519, filed November 15, 1951, the all-plastic seals of thisinvention need not necessarily be made between a conductive plasticcomposition and the insulator plastic from which it was made. it can,indeed, involve a joint between substances which are chemically quitedifferent. Of course, the two plastic materials, conductor andinsulator, should be chosen so as to have similar thermal coefiicientsof expansion or else undue strains may be set up in the joint duringservice. The required degree of similarity will be determined by theconditions of temperature cycling to which the joint will be exposed.

In any particular case the determination of a reasonable correspondenceof thermal coeflicients of expansion will call for the use of ordinaryengineering judgement. In this connection it is well to note that if oneof the plastics 1s relativelyyielding or is comparativelythim a largedifierence in'coefiicient of expansion can betole'rated.

. Aside from the use of the special technique (described in'my latternamed copending application of Myron Q A- Coler and Arnold S, Louis) forbonding together chemically dissimilar plastics, any of several methodsmay .be used to secure a bond between an'electrically conductive plasticcomposition and its corresponding parent insulator plastic or onechemically similar to" it. I 'For instance, the two molding powders maybe compression molded together by laying down the two powders oneabovethe other or.side by side in the mold. I 1

speak of this process as co-molding.

technique against an insert of the other.

Already moldedpieces of the two plastics may be ef fectually joined bywetting .the faces to be joined with y a solvent, pressing the two facestogether and keeping them under pressure until the solvent'dries outsufficiently to make afirm bond. 7 V V 'lnjanother process, moldedpieces of'thermoplastic type may be'joined by heat sealing. Heat may beapplied by contact with a heated tool or by any convenient method ofgenerating localized heat, Particularly useful is the, highfrequencyinduction heating technique. By this means heat may begenerated directly in the conductive plastic or it may be more strictlylocalized to the joint area by locating there a small piece of metal orby coatingthe surface of the plastic with metal by any of several knowntechniques.

In Figure 1 there is shown a tubular body plastic 2 integrally'bonded tocaps 4 and of electroconductiveplastic composition 4.-,The caps completethe electrical circuit between an external circuit and theelectrochemical system within the case formed by the tubular body 2 andthe caps 4 and 6. A standard metal terminal 8 may be insert molded intoelectroconductivecap 4 to provide a means to connect the cap 4 toexternal circuits. For purposes of illustration a metallic coating towhich a lead may be soldered or to which pressure co'ntact may be made,is shown as the terminal 14. In most applications it is desired that thecoating be inert electrochemically to the constituents of the batterysystem. Metallic coating 4 is applied to a surface of conductive plastic6 by any of several well known techniques such as sprayed metal,electroplating, thermal evaporation or by application of a conductivelacquer. To this coating electrical contact .Again, one plastic may bemoldedfby any convenient 20 of insulator 6 consisting .rnay be made, forinstance, by pressure contact or by soldering.

A preferred coating method is disclosed in Figure 2 wherein a heatedpiston 20 presses finely divided metal powder 22 into the surface 24 ofconductive plastic 26. Heater'element 28 is energized by a source ofelectrical energy such as generator 30. his preferred that athermoplastic plastic base be employed. The piston should be heated to atemperature sufiicient to soften the surface of the plastic. Thepressure is not critical; a pressure of 2000 pounds per square'inchbeing satisfactory.

Obviously the various methods of obtaining elec-' trical contact whichhave been described and others which will occur'to those skilled in theart may be used in any convenient combination.

I have found that a piece of electrically conductive plastic compositionwhen used as an electrode in conf tact with an electrolyte will developa potential of a similar order to that of an electrode of the pureconductive material which was used in the plastic composition.Accordingly, the electrode substances of an electrochemical system canbe mixed in finely divided form with a suitable insulator plastic toform an electrically conductive plastic composition which compositioncan be used to make structural elements of this invention which, at thesame time, serve as'electrodes of an electrochemical system.Alternatively, a conductive plastic maybe chosen which is inert to theelectrochemical system and then the plastic may be coated with the anodeor cathode ma terial of the electrochemical system. The types of casingjust described can be used to enclose any electrochemical systemprovided the insulator and conductive plastics are chemically resistantto its components. Cell case structures of the second type' justdescribed are particularly advantageous for the construction of verycompact cells for applications requiring long life at low current drainsor short life at high current drains.

Referring again to Figure 1, cylinder 2 of insulator 7. plastic isclosed at either end'with discs 4 and 6 of conductive plastic. Whendiscs 4 and 6 are made from a conductive plastic c'omposition containinga properly selected, comparatively inert metal, the casing may be usedto contain practically any electrochemical cell system. Closure may bemade by heat or solvent seal. It will be observed'that closure must becompleted after the cell components, including electrolyte, have beeninserted. Furthermore, contact will generally be made to the inside ofthe conductive casing ends by means of simple pressure against the cellcomponents. 7

Under these circumstances, induction heating, is preferred to effect atleast the final seal because by this means heat may be generated quicklyand locally at the bonding region without overheating" the cellelectrolyte or the other inner components of the cell. This is shownpictorially in Figure '3 where a two-turn 'coil of copper tubing 40 isfitted closely around the region of the final bond 42. The tubingisconnected to a source of radio 'frequency electrical energy. The speedand localization of this energy release can be increased if cap 43 iscoated with metal 45. c

Specifically, I have made cells of the zincpotassiumhydroxide-mercuricoxide type commonly known as Ruben-Mallory cells as follows: Cylinder 2(Figure 1) was a tube of polystyrene 0.46 inch high, 0.63 inch inoutside diameter and 0.50 inch in inside diameter. To this was firmlybonded a disc 6, 0.08 inch thick, made of an electrically conductiveplastic" composition containing about 10% silver and polystyrene; 'Inthe cup thus formed were placed a mercuric oxide depolarizer pellet 10,barrier disc 5, anode assembly 7 and electrolyte identical with thoseemployed in commercial .cells of similar type. The dimensions of thecylinder had been chosen so that these parts would be subjected tomechanical compression during the next step of cell assembly. A seconddisc 4, similar to the first, was then pressed on top of the cup and itscontents and'the whole positioned inside a close fitting two-turn coppercoil 40 as shown in Figure 3 connected to a generator of high.

frequency electric current, so that the coilclosely 'sur rounded thejunction between cup and disc. The current was turned on for 10 seondsduring which time 260 milliamperes at volts were drawn from the platecircuit ofthe source. The assembly was cooled under pressure.

Many cells assembled in the above described fashion have been tested andfound to have operating characterisics fully equal to preexistingcommercial cells and at the'same time free of gross electrolyte leakingwhichis a serious problem with metal encased cells when they are storedfor long periods of time.

; Likewise, I have found that similar structures in which theinsulatorplastic is polymonochlorotrifiuoroethylene are well suited forencasing highly corrosive electrochemical systems such as thosecontaining hydrofluoric acidj When a compact cell possessing long lifeatlow current drain is desired, the height of the cylinder Zcan be reducedgreatly. Discs 4 and 6 can be made from an electrically conductiveplastic composition prepared by incorporating in a suitable insulatorplastic the appropriate electrode materials for the electrochemical cellsystem in question. The interior of the cell is filled with electrolyteand depolarizer.

A cell of this type is shown in Figure 4 wherein a disc 50 was formedfrom a thin wafer of a conductive plastic composition containing about92% polymonochlorotrifiuoroethylene and 8% acetylene black. On thislayer a wafer 51 of porous polymonochlorotrifluoroethylene impregnatedwith a slurry of finely divided manganese dioxide in a solutioncontaining about 20% ammonium chloride was placed. Around this wasplaced a ring shaped wafer 52 of polymonochlorotrifiuoroethylene. On topwas placed a wafer 53 of a conductive plastic composition containingabout 90% polymonochlorotrifluoroethylene and finely divided zinc metal.The cell was sealed together by induction heating. The assembled cellwas liquid-tight, showed good storage properties and developed apotential of 1.3 volts.

The encasement of a standard zinc-carbon cell 71 in a sealed plasticcase of this invention is shown in Figure 5 wherein an insulatingplastic tube 72 encircles the battery 71 and conductive plastic caps 73,74 complete the unit. The caps are provided with contact making surfaces75 and 76. It is preferred that a metallic coating be applied tosurfaces 75 and 76 as discussed earlier.

The many embodiments of the invention disclosed herein are intended tobe descriptive of what I currently believe to be the preferred versionand are not intended to be limiting in any sense for it is appreciatedthat those skilled in the art may make many changes and adaptationswithout departing from the spirit of the invention and it is thereforemy intent that the appended claims cover all such changes andadaptations as fall within the spirit and scope of the presentinvention.

I claim:

1. A dry cell consisting of an electrochemical system enclosed in atubular insulator organic plastic member having sealed to each end aconductive plastic cap, said electrochemical system having a cathodemember in electrical contact with one of said conductive organic plasticcaps and an anode member in electrical contact with the other of saidconductive organic plastic caps, the

conductive organic plastic being chemically and electrochemicallynon-reactive to said electrochemical system.

2. The dry cell of claim 1 wherein said cathode memoer is adherentlydeposited on the enclosed face of one of said caps and said anode memberis deposited on the enclosed face of the other of said caps.

3. A dry cell of claim 1 having deposited on the exposed faces of saidconductive plastic caps 21 contact making surface of a highly conductivematerial, said material being chemically and electrochemicallynon-reactive with the components of said electrochemical system.

4. A dry cell having an anode portion consisting of a conductive organicplastic material containing an anodic material and a cathode portionspaced therefrom consisting of a conductive organic plastic materialcontaining a cathodic material, an electrolyte disposed between saidanode and said cathode, and an insulating organic plastic portionenclosing said electrolyte interposed between said anode and saidcathode portions and sealed thereto.

5. The dry cell of claim 1 wherein said conductive plastic is formed ofa body of organic molding plastic having a fine lacy network of solidconductive material extending therethrough providing a multiplicity ofconductive paths through said body.

6. The dry cell of claim 1 wherein said conductive plastic is formed ofa body of organic molding plastic having a fine lacy network of solidconductive material extending therethrough providing a multiplicity ofconductive paths through said body and the exposed faces of saidconductive plastic caps have deposited on their exposed faces a highlyconductive contact making surface.

7. The dry cell of claim 4 wherein said conductive plastic is formed ofa body of organic molding plastic having a fine lacy network of solidconductive material extending therethrough providing a multiplicity ofconductive paths through said body.

References Cited in the file of this patent UNITED STATES PATENTS2,572,017 Ellis Oct. 23, 1951 2,684,397 Gottschall July 20, 19542,686,214 Arbogast Aug. 10, 1954

1. A DRY CELL CONSISTING OF AN ELECTROCHEMICAL SYSTEM ENCLOSED IN ATUBULAR INSULATOR ORGANIC PLASTIC MEMBER HAVING SEALED TO EACH END ACONDUCTIVE PLATIC CAP, SAID ELECTROCHEMICAL SYSTEM HAVING A CATHODEMEMBER IN ELECTRICAL CONTACT WITH ONE OF SAID CONDUCTIVE ORGANIC PLASTICCAPS AND AN ANODE MEMBER IN ELECTRICAL CONTACT WITH THE OTHER OF SAIDCONDUCTIVE ORGANIC PLASTIC CAPS, THE CONDUCTIVE ORGANIC PLASTIC BEINGCHEMICALLY AND ELECTROCHEMICALLY NON-REACTIVE TO SAID ELECTROCHEMICALSYSTEM.